day06/lanternfish.sh

   1 #!/bin/bash
   2
   3 set -u
   4 set -e
   5
   6 declare -a fish
   7
   8 filename="${1:-example.txt}"
   9
  10 exec 3<"$filename"
  11
  12 OLDIFS="$IFS"
  13 IFS=","
  14 read -u 3 -a fish
  15 IFS="$OLDIFS"
  16
  17 for (( d=1; d<=80; d++ )); do
  18     start_fish_count=${#fish[@]}
  19     for (( i=0; i<$start_fish_count; i++ )); do
  20         if [ ${fish[$i]} -eq 0 ]; then
  21             fish+=(8)
  22             fish[$i]=6
  23         else
  24             ((fish[$i]-=1)) || fish[$i]=0
  25         fi
  26     done
  27 done
  28
  29 echo "After 80 days there are ${#fish[@]} fish"